Proper definitions for MHz and mHz, etc.

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David Tanks

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May 17, 2025, 6:38:37 AM5/17/25
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Just more stuff to keep us confused (or to keep us straight on definitions)!

David AD4TJ
----- Forwarded Message -----
From: Dave Daniel via groups.io <kc0wjn=gmai...@groups.io>
Sent: Friday, May 16, 2025 at 09:21:14 PM EDT
Subject: Re: [tinysa] What accessories do I need for a TinySA Ultra?

Dave, W0LEV, is correct. The metric prefixes are well-defined. See 


for a list of them. One of the ones that people screw up is milli (m) vs. mega (M). When mHz (or mhz) is typed instead of MHz, most of us can infer the correct prefix and unit. But in actual scientific and engineering work, accuracy in notation is very important, so we strive to use the correct notation. The difference between milli (m) and mega (M) is *nine* (10E9) orders of magnitude.

The unit abbreviation is also screwed up by many people. The unit "Hertz" is properly abbreviated as "Hz" and not "hz" and named after Heinrich Hertz, who was the first physicist to prove the existence of electromagnetic waves after Maxwell predicted them mathematically. We pay tribute to Hertz's pioneering work by capitalizing the abbreviation Hz. Other examples are J for Joule, W for Watt, O for Oersted, T for Telsa (the physicist, not the vehicle), V for volt, etc., etc., all named after the scientists who first discovered or identified the quantity in question. While many users of the tinysa are not engineers by vocation, they have to know or learn the technical principles involved with using spec ans and it behooves us (at least IMHO) to get the notation correct when communicating technical information.

There are other units the abbreviations for which people routinely mistype. The difference between "S" (Siemens) and "s" (seconds) comes to mind.

One of the basic techniques for solving mathematical equations in scientific work is to perform unit analysis as well as the mathematical calculation. Unit analysis involves ignoring the numbers and looking at the units to make sure that the units agree on both sides of the equation. If one starts with something such as "Volts/meter" on the LH side of the equation and unit analysis results in "meters/second" on the RH side of the calculation, one knows that one has miscalculated. Using the correct abbreviations for the units involved is key to accomplishing that effort.

The above is just my take on this stuff after working for 30+ years as an embedded systems design engineer in the IBM computer world of engineering. Worth 25 cents, taking into account inflation.

DaveD
KC0WJN


On Fri, May 16, 2025 at 20:16 Mike C. via groups.io <mg=mgte...@groups.io> wrote:

Hate to burst your bubble Dave, but the HP-3561A , in their documentation, refers to the low frequency coverage (micro Hz) as uHz, and how about kHz. So, yeah, mHz for "mili Hz" works for me but hey I'm only a retired technician. BTW electron flow is from (-) negative to (+) positive, but the engineers I worked with called it "hole flow". ??? I guess they stand on an overhead bridge and watch the spaces going the opposite way than the cars.

Clip from pdf of HP's 3561A:

Just sayin'

Mike C. Sand Mtn GA


On 5/16/2025 6:34 PM, W0LEV via groups.io wrote:
Yea, Don, get the newbies to use proper abbreviations!  I've called it out many times, but it seems to fall on deaf ears and clearly never reaches the gray matter.  What really gets my goat is "mhz".  What is mhz?  MilliHertz?  Nothing the typical amateur deals with delves into the milliHertz range!  Further the proper abbreviation for Hertz is Hz, not hz!  Should I give up?

Dave - WØLEV

On Fri, May 16, 2025 at 5:49 PM Donald S Brant Jr via groups.io <dsbrantjr=gmai...@groups.io> wrote:
On Thu, Mar 20, 2025 at 04:17 PM, sdegroff wrote:
All references when not given are 0db = 1w
My observation is that very few people use units of dbW even when working at high power, dbm (relative to 1 milliwatt) being far more common. 
If a colleague started using dBW I would ask them why as I see no good reason for it, it is likely to cause confusion.  Like 1000X level confusion.
 
In the RF world, if something is written as "xdB" it is NOT a power level, it is a power ratio, or actually 10log of that ratio. 
 
The TinySA power specs all use dBm AFAIK.
73, Don N2VGU


--
Dave - WØLEV


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